Start-stop telegraph



March 1937- R. G. GRIFFITH START-STOP TELEGRAPH 4 Sheet-Sheet 1 Filed May 29, 1935 March 30, 1937. R. G. GRIFFITH START-STOP TELEGRAPH Filed May 29, 1935 4 Sheets-Sheet 2 March 30, 1937.. R. G. GRIFFITH START-STOP TELEGRAPH Filed May 29, 1955 4 Sheets-Sheet 3 I i E? MN 5% .1 s 3 e w. II

V EM 5 E W WW H 1 d March 30, 1937. R. G. GRIFFITH START-STOP TELEGRAPH 4 Sheets-Sheet 4 Filed May 29, 1935 Nw ww R mm no @Q mm E Patented Mar. 30, 1937 PATENT OFFICE START-STOP TELEGRAPH Ronald George Grifli tli, Ilpper Warlingham,

Eng and Application May 29,

1935, Serial No. 24,153

In Great Britain June 19, 1934 Claims.

This invention relates to start-stop telegraph systems and is particularly concerned with the transmitting and signal recording mechanism of start-stop printing telegraphs employing an equal length code. In such systems the transmission of each character involves the sending of a starting impulse, a number of permuted code impulses followed by a stop impulse.

The object of the invention is to provide a o mechanism of simple construction in which in the transmitting mechanism a minimum distortion of the transmitted signals shall be produced with a given amount of manufacturing irregularities. Then a greater part of the margin of signal distortion provided for in the receiving apparatus may be utilized to allow for the distortion produced in'the connecting media, that is to say, a telegraph line or the radio link. Furthermore, the invention aims at providing a mechanism of simple construction and yet foolproof in operation which will handle successfully input signals of a widely distorted character.

According to the present invention, a rotating member, such as a cam shaft, is provided for the transmitter or for the receiver and is arranged to form or to control a signal member arranged to select each transmitted impulse mechanically or at the receiver to actuate selecting mechanism or re-transmitting mechanism, and that rotating member is driven at such an angular velocity that it executes one revolution in a time equal to one or more signal impulse periods but not exceeding the time of all the code impulses of one complete character signal. Both at the transmitter and receiver it is preferred for the rotating member or cam shaft to be driven so as to complete one revolution or a half revolution in the time required for transmitting, selecting or re-transmitting each permuted code impulse. 'Thus, both at the transmitterfand receiver a selecting cam shaft is provided, arranged when released to make a predetermined amount of angular motion, usually one complete revolution or a half revolution. At the transmitter the selecting cam shaft is associated with means for operating different selecting devices provided for dealing with successive impulses at regular intervals in its rotationand the transmitting cam shaft is geared to the selecting cam shaft with such a ratio that the transmitting shaft rotates more quickly than the selecting cam shaft, and preferably so that it makes one revolution during each angular movement of the selecting cam shaft equivalent to one signal impulse. In other words, one revolution or a half revolution of the transmitting cam shaft is equal to an exact multiple of the impulse sub-multiples of the selecting cam shaft.

Similarly at-the receiver the signal receiving I member is a cam shaft geared to the selecting cam shaft of the selecting mechanism which bears cams or equivalent means for operating permutation bars or devices directly or indirectly in either of two different directions, depending upon the setting of a control device, the cams or other equivalents being so arranged in relation to the members which they engage as to ensure successive operation of the group of permutation bars or devices at regular intervals in the angular motion of the selecting shaft. This shaft is likewise caused to effect a certain angular. motion, usually a half revolution when released and the cam shaft which serves as a mechanical relay member is geared to it so that the mechanical relay member rotates more rapidly than the selecting cam shaft and preferably completes one revolution in the time corresponding to the reception of one impulse of a given character signal. In both the transmitter and receiver the cam shaft may be mounted so as to be capable of motion in the direction of its axis and capable of taking up one of twopositions corresponding to the two kinds of impulses to be transmitted. The invention may be applied to various kinds of start-stop transmitters, such as keyboard controlled apparatus, tape controlled apparatus and regenerative repeating apparatus and so forth. The operation of the transmitter in any event controls the successive axial positions of the cam shaft and the latter may then be provided with a cam so that at each revolution of the shaft corresponding to one impulse of a character signal, the cam, depending upon the axial position of its shaft, co-operates to move a contact-making member in one direction or the other for effective transmission of the two forms of impulse constituting the complete series representing a transmitted character signal.

At the receiver, the cam shaft constituting the mechanical relay member, may be arranged to co-act by direct contact with the signal recording member, which will usually be a single receiving magnet, in such a manner that the cam shaft will be positioned due to its own driving power as a result of contact with the armature of the receiving magnet. This armature forming the co-operating part of the signal recording member is formed with or controls a cam face or cam faces on which a member carried by the cam shaft is caused to make contact during rotation of that shaft. It is preferred, however, to construct the mechanism so that all the coded impulses are selected so that the cam shaft maintains one 'or other of its axial positions when dealing with the next subsequent impulse of similar character to one last recorded so as to eliminate the necessity for re-setting or re-positioning for every impulse; in other words, the cam shaft or mechanical relay member only alters its axial position when an impulse of different character from the last is received. The period during which the signal recording member exercises control over the mechanical relay member represents only a small fraction of the total angular movement which the relay member makes while rotating during the time required for the recording of one impulse. Consequently, the extent of the time of interference when the signal recording member, that is the armature of the receiving magnet, is not free to move under the control of the incoming signals is of minimum duration.

The selecting cam shaftof the receiving mechanism is arranged to operate different selecting devices provided for recording or otherwise dealing with successive signal impulses at regular intervals in its movement. Since the amplitudes of movement of the mechanical relay member and the selecting cam shaft are proportional to one another, the setting operations effected by the signal recording member may be timed with precision in relation to the selecting operations. This degree of accuracy enables the selecting of the permutation bars of the receiver to occupy a 3 larger period of time.

In order that the invention may be clearly understood and readily carried into effect, it will be more fully explained by way of example in its application to a keyboard controlled printing telegraph transmitter and to a single magnet receiver in which the stored or recorded incoming character signals are represented by the positions of a number of permutation bars, with reference to the accompanying drawings, in which:-

5 Figure 1 is a side elevation of the essential parts of the transmitter;

Figure 2 is a perspective view of the main parts of the transmitter;

Figure 3 is a perspective view showing the essential parts of the receiving apparatus, and

Figure 4 is an end elevation of the selecting mechanism of the receiver.

Referring to Figures 1 and 2, the selecting cam shaft is shown at I and .the five selecting cams at 2', 2 2, 2 and 2 with the start cam at 2. The shaft is intermittently driven through a friction clutch or other coupling means, capable of slipping, from a shaft constantly driven at a suitable speed, but when a character is transmitted by the depression of any key, a mechanism is arranged to withdraw the usual detent 3 from a stop surface 3 carried by the shaft I, so that the latter is frictionally or otherwise driven through one complete revolution whereupon the detent holds it up again. Thus, the shaft l makes one complete revolution for each character transmitted. Actually, before the five code cams 2* 2 come into operation, the additional start cam 2 first of all sends a starting impulse and when the five cams 2' -2 have operated, a stopping impulse may be sent.

One of the key levers is indicated at 4 and each has an extension 5 engaging a notch 6 in a lower extension of the corresponding selector frame 'I.

There are consequently a number 9f elector frames 1 equal to the number of characters provided on the keyboard. When a key is depressed, the extension 5 draws down the corresponding selector frame 1 against the action of a tension spring 8 and, as a result, certain internal projections 9 on the frame I operate upon a series of vanes Ill carried on spindles II, the frame I at this time being guided on fixed pins IL The number of the vanes l0 provided depends on the number of code elements used. In the case illustrated five are provided. As a result, accord-- ing to theparticular combination set by the key which has been depressed, certain of the five vanes III are turned clockwise and certain of them counter-clockwise.

Spaced from the frames 1 along the spindles I I, there are further five frames 98', 98", 98, 98* and 98, each of which has one projection corresponding to those shown at 9 in position to be engaged by one of the vanes l0. Thus, these additional frame MI -98 each corresponds to one of the five vanes Ill and by means of the vanes each will be caused to take up an upper or lower position at each selection on the depression of one of the keys 4. These five additional frames have projections to the rear, shown at l3, H, which are moved to the upper or lower position with the frame in question.

A cam shaft l5, bearing an eccentric earn it, is

also released and actuates a lever ll pivoted at Ill. The lever I! has a pair of horns I9, 20 cooperating with the cam IS, the former providing for positive forward motion of the lever l1 and the latter for positive return motion. Thus, at each selection the lever i1 is moved forward and five further levers 2| 2I*, each carried on a pin l1 projecting from the upper end of the leverll, are thrust forward and are caused to co-operate with the projections l3, ll of the corresponding permutation frame Sa -98. Each lever 2| --2 F has two forward projections 23, 24 while there is a common transverse bar 22 extending in front of all the levers. The purpose of the transverse bar 22 is to engage with a pointed projection 25 on each of the permutation frames so that if it chances that any one of the permutation frames has not been quite fully moved to the upper or lower position, the bar 22 engages above or below the corresponding projection 25 and positively thrusts the permutation frame into its full upper or lower position. If a permutation frame is in the full upper position then the corresponding projection 24 abuts against the projection I 4 of the corresponding frame so that the lever 2| 6 is rocked upward into the position seen at 2| c in Fig. 1. If previously it werein the position shown at 2| in Figure 1 it moves as described and rocks over the pivoted connecting member 26 and consequently moves the corresponding selector bar 21 from the position shown towards the left. Of course, if the permutation bar is already in that position, no movement takes place. Ii, however, the corresponding permutation frame is in the lower position, then the projection 23 abuts against the upper projection l3 of the corresponding permutation frame and the lever 2| '--2l is rocked counter-clockwise into the position shown at 2l in Figure 1.

The gear for tripping the shaft l5 and the detent 3 is controlled from an additional sliding frame 99. There is an additional vane I00 below the five vanes l0 and the projections 9 on the frames I are so arranged that when any key.

lever is depressed, the vane N10 is tilted, its shaft IOI being rocked slightly counter-clockwise. This causes the additional frame 99 tobe thrust down against the tension of the spring I02. Thenthrough the arm I03, a detent I04 is de- 5 pressed releasing the stop surface I05 on the shaft I5. The latter is driven and, at a certain point in its revolution, .a cam I05 depresses the right hand end of the detent 8 which is pivoted at I01 so that the shaft I is released. In due 1 course, the arm I03 is restored by a cam I08.

The result therefore on depressing a key lever 4 is first of all that the five selector bars 21=--21 are each set either in the position to the right as shown at 21 in the drawings, or in a position more to the left as shown at 21 with the result that a projecting tail 28 *--28 of each selector bar either registers with a rear extension 29 of the corresponding selecting lever 30-30 or the tail 28 is moved to the right with the selector bar 21 and leaves the projection 29 free.

As illustrated the selecting devices consist of five levers 3I'I**---3Il each pivoted at 3I and each allocated so as to co-act with the corresponding selecting cam 2 2. There is an additional lever also pivoted at 3I and-co-operating with the cam 2 for giving the start impulse but not cooperating with any selector bar such as 21 --21. When the shaft I starts rotating, the cam 2 cooperates with the corresponding selecting lever 30 30, the latter is allowed to fall down the step of the cam 2 and thus move towards the centre of the shaft I, being urged in that direction by the pressure of a common pivoted member 32 which has a bar 33 extending over all five of the selecting levers 39 -30 and over the lever 30. The common member 32 is pivoted at 34 and tends to be moved counter-clockwise by a tension spring 35; As the levers 30-30 are all in their lower positions at this time, the member 32 is rocked by the Spring 35 and the bar 33 descends to give the start impulse as will be described below. The cams 2 ---8 in succession come into the positions in which they tend to lift the corresponding levers 30 --30'= and whether they are able to lift them or not depends on the position of the respective selector bars 21--21. In Figures 1 and 2, the selector bar 21 isshown displaced to the right with its tail 28 immediately above and therefore in registration with the extension 29 of the lever 30. Thus when cam 2 comes into position to lift this lever, the right hand end of the latter cannot rise and, therefore, its left hand end is forced up and lifts the common bar 33. The other four levers 30, 30 30 and 30 are not restrained at their right hand ends by the tails of their selector bars, so that when their respective cams come into action, their right hand ends are free to rise and these levers do not lift the common bar 33.

60 A spur wheel 36 is fixed to the shaft I and engages with a small pinion 31 fixed to the transmitting cam shaft 38. The gear ratio is such that the transmitting cam shaft 38 makes three and a half revolutions for each character transmitted, that is one half a revolution for each code impulse, one half a revolution for start and one half a revolution for stop. The shaft 38 is mounted so as to be slidable in the direction of its axis and carries a cam 39 arranged to operate selectively one or other of a pair of arms 40, H

of a pivoted contact member 42. As can be best seen in Figure 2, the arm M is cranked so that the ends of the arms 40, 4| are staggered or displaced relatively to one another in the direction 0 of the axis of the transmitting shaft 38.

As seen in Figure 2, this shaft is moved in the axial direction depending upon the position of the common bar 33. The forward end of the member 32 engages a fork in a bell crank 43 which is pivoted about an axis 44 at right angles to the axis of the shaft 38. Thus, when the selecting cams 2 allow the member 32 to rock slightly counter-clockwise, the forward end of the latter descends and through the bell crank 43 moves the shaft 38 to the left in Figure 2; then the cam 39.

presses against the arm 4| and the member 42 is rocked counter-clockwise and, at its upper end, makes contact between members 45 and 46 which results in sending an impulse of one sign, for example a marking impulse, to the line. As the cams 2 and 2 do not lift the bar 33, the contacts 45, 45 remain closed and two more marking impulses are sent. As, however, the next selector bar ,21 prevents the lever 30 from lifting at its right hand end, it lifts the common bar 33 and causes the member 32 to rock clockwise and the member 32 through the bell crank 43 moves the transmitting shaft 38 back to the right until the cam 39 is opposite the arm 40 and during the following half revolution of the shaft 38, the cam 89 presses on the arm 40 thereby swinging over the member 42 and bringing the contacts 45 and 41 together so as to transmit to the line an impulse of opposite sign, that is to say, a spacing impulse. Finally, the cam 2 completes a whole revolution and lifts the bar 33 to send the stop impulse. The result is that when a key is depressed, the shaft I makes a complete revolution, the shaft 38 makes three and a half revolutions and the cam 39 during those revolutions makes five code contacts in addition to the start and stop", so that the impulses are sent to the line representing the combination which corresponds to the character whose key has been depressed.

These five code and the start and stop impulses passed to the line affect, in turn, the single magnet 48 of the receiving apparatus shown in Figure 3 so that according to the impulses this magnet draws down its armature 49 or leaves it in the raised position. This armature is formed with an upstanding projection 50 and with a hook 5I at its forward end with an inclined cam surface 52 at the right side. The main selecting cam shaft is shown at 53 in Figures 3 and 4 and is intermittently driven through a coupling 54 which rotates at steady speed but is capable of slipping. Actually, as illustrated, the'shaft 53 is allowed to start when a character signal arrives,

to turn through half a revolution and is brought to rest.

The mechanical relay member consists of a spindle 55 geared to the shaft 53 through a pinion 58 and spur wheel 51, the gear ratio being such that the spindle 55 executes three revolutions for each character signal received. This spindle 55 is mounted so as to be capable of sliding in the direction of its axis without however the wheels 56 and 51 coming out of engagement. The spindle 55 carries a two part cam 58 in such a position that when the spindle 55 is in one axial position, the cam 58 can engage an arm 59 of a rocker 60 and when in the other axial position it can engage the other arm 5| of the rocker 60. Thus, the arms 59 and BI are staggered or relatively displaced in the direction of the axis of the spindle 55 by an amount equal to the amount of axial movement of the spindle 55.

The axial movement of the spindle 55 is produced by its own driving force by means of a pair tions and allocated so as to be able to co-act with the inclined edge of the hook 5! of the armature 55, the result being that if the armature 55 is attracted and thereby the hook 5| drawn down during the time allocated to the reception of one impulse, the camming action between the inclined surface 52 and the pins 52 causes the spindle 55 to be moved to the right in Figure 3 and this corresponds to the position it takes up for impulses of one polarity. If, however, an impulse of the opposite polarity arrives, the armature 45 is released and the hook 5| moved up out of the path of movement of the pins 52. In that event, however, a bell crank 55 moved yieldingly forward by a spring 54 brings a similar inclined surface on its hooked end 55 into the path of movement of the pin 52 by which means the spindle 55 is brought back again to the left in Figure 3. It may be mentioned here that the spindle 55 is only moved if an impulse of one polarity is followed by an impulse of the opposite polarity. If, on the other hand, two impulses of the same polarity arrive, the spindle 55 having been moved due to the first impulse, remains in that position upon the reception of the second. Actually in a printing telegraph the bell crank 53 may be arranged to serve as a space setting lever. It will be noticed that it is set in a, different plane to the armature so that the inclined edges overlap and diverge in the direction of rotation of the pin 52. However, the two parts may be constructed so that when the hook 5| is moved to the operative position when the magnet 45 is energized, it displaces the hook from the operative position. In other words, the two inclined edges of the hooks 5| and 55 constitute a gate for the setting pins 52. Of course, the spring 55 must be strong enough to 0 cause the hook 55 to impart the necessary sliding return movement to the spindle 55.

By making the end of the armature 45 of the single magnet 45 in the form of a fork, the two limbs of which respectively co-act with the setting pins 52 extending in opposite directions from the shaft 55, then one limb of the fork may be shaped to move the shaft55 one way and the other limb the other way along the axis of the shaft. Again, the member which sets back the shaft 55 into the spacing position, may be arranged to co-act with the setting pin 52 at a convenient time interval in advance of the engagement of the armature 55 with the setting pin so that the shaft 55 is reset into the spacing" position before it is engaged by the magnet, armature.

The rocker 55 is fixed to a sleeve 55 which can turn on an axle 51. At its opposite end, the sleeve 55 is fixed to a rocking cradle 55 provided with side members 55, 15 which lie outside and against the outer surface of certain levers II, I2. The levers II and I2 are in five pairs; each of these levers are slotted or notched at their lower ends as shown at 15 and these notches each engage one or other of a pair of opposite pivot spindles I4, 15 on to which they are held respectively by the side members 55, 15. Each pair of levers II, I2 engages at their upper ends in one of the five permutation bars I5.

The selecting cam shaft 55 carries five pairs of selecting cams 'II. These cams are in pairs because in the particular construction illustrated, it will be recollected that at each release the shaft 55 only executes a half a revolution, that is to say, a complete revolution corresponds to of pins 52 projecting from it in opposite direcof the cams II is in the plane of one pair of levers II, 12, the latter being provided with projections I5 for co-operation with the cams II. The cams II, as seen in Figure 3, are angularly spaced so that during the time corresponding to each signal impulse, that is to say, during the time of half arevolution of the spindle 55, one of the cams 1! comes into the operative position co-acting with the projections 15. If that particular impulse has caused the armature 45 to be drawn down, then the hook 5i comes into the path of the setting pins 52 and the spindle 55 is either pushed to the right in Figure 3, or if already in that position, remains there. This brings the cam 55 opposite the arm 5|, causing the rocker 55 and the cradle 55 to rock, clockwise. If, however, an impulse of the opposite polarity arrives, the hook 55 moves the spindle 55 to the left so that the cam 55 is placed opposite the arm 55 of the rocker 55 and cradle 55 are rocked counter-clockwise. Actually the former condition is illustrated in full lines in Figure 4. The rocking of the cradle has caused the side member 55 to rise and the other side member to fall. Therefore, the cam 11 acting on the projections 15 causes the lever II to turn about the pivot I4 as the side member 55 prevents it leaving the pivot and pushes over the corresponding permutation bar 15 to the left. The opposite lever I2 is released by the side member I5 and consequently can turn about its upper end as a fulcrum and with its lower end moving with respect to the pivot I5. The result is that this particular permutation bar I5 moves to the left.

Thus, after three revolutions of the spindle 55 each of the five permutation bars I5 has been caused to take up its position to the right or to the left; then the shaft 55 has turned through half a revolution and will be brought to rest in a manner which will be described below. The five permutation bars 15 are thus set up to represent a combination corresponding to the char acter signal received and this setting of the permutation bars I5 can be used to actuate a printing mechanism, recording mechanism or retransmitting mechanism.

Each character signal is preceded in the usual way by a starting impulse which causes the magnet 55 to be energized and to trip the starting device. This starting device consists of a starter shaft I5 driven through a clutch 55 capable of slipping and actually subjected to a lighter pressure than the clutch 54. Normally the shaft I5 is prevented from turning during non-signalling periods by a radial stop 5| fixed to it and engaged by one arm of a bell crank lever 52. The other arm of the bell crank lever 52 carries a foot 55 slidably mounted on the bell crank 52 and having an associatedpart 55 bearing against a cam 55 on the shaft I5. The part 55 is pivoted at 55 and is held against the cam 55 by a spring 51. The bell crank lever 52 is drawn towards the shaft 15 by a spring 55.

On reception of the starting impulse, the projection 55 engages the end of the foot 55 so as to rock the bell crank lever 52 and release the radial stop 5|. The latter therefore commences to rotate with the shaft I5 and immediately the cam 55 causes the foot 55 to slide along the bell crank lever 52 so that its extension misses the projection 55 of the armature 55, with the result that when the bell crank lever 52 returns to its normal position under the action of the the reception of two character signals. Each' spring 89, it does not interfere with the armature 49. A further cam 89 on the shaft 19. acts on a triangular member 99pivoted at 9| so as to rock the latter and cause it to act on the tail 92 of a detent 93 drawn down normally by a spring 94 so that a hook 95 at its end engages a radial stop 96 fixed to the shaft 53. As soon as the member 90 passes the tall 92, the spring 94 pulls 10 the detent 93 down again and in the meantime the latter has released the stop 96 and the shaft- 53 begins to rotate and to drive the spindle 55. This goes on until the shaft 53 has turned through half a revolution when the second radialstop 91 is caught up by the detent 93 and the whole mechanism comes to rest again. During the cycle, the spindle 55 has made three revolutions, the five impulses have been received and have resulted in setting of the five permutation bars l6.

The trian'gularmember 90 forming the lifting device for the detent 93 may be carried on a mounting which is adjustable around the axis of the starter shaft 19, so as to be capable of operating the detent 93 in any position to which it may be adjusted. By this means, the starting and the selecting cam shaft 53 can-be timed with respect to the moment of receiving the starting impulse so that the selecting cams can also be timed with respect to the moment of receiving the starting impulse without affecting their timing with respect to one another.

I claim:--

1. In a start-stop telegraph, the combinatio of a selecting cam shaft, means for intermittently rotating said cam shaft, a single rotary member arranged to effect the mechanical selection of each of the code impulses of the signal permutations' and connecting gearing between said 40 rotary member and said cam shaft, the ratio of said gearing being such that one revolution of said rotary member occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal.

2. In a start-stop telegraph for working on an equal length code, the combination of a selecting cam shaft, means for intermittently rotating said cam shaft, a single rotary member arranged to effect the mechanical selection of each of the code impulses of the signal permutations and connecting gearing between said rotary member and said cam shaft, the ratio of said gearing being such that said rotary member is rotated by an amount of half a revolution in the time occupied by each permuted code impulse.

3. In a start-stop telegraph, the combination of a selecting cam shaft, means for intermittently rotating said selecting cam shaft, a second cam shaft mounted to rotate and to be shifted .in the direction of its axis into either of two positions depending upon the kind of impulse dealt with, a cam mounted on said second cam shaft, an actuating member formed with two projections located to co-operate with said cam respectively in the two axial positions of said second cam shaft and connecting gearing be,- tween said two cam shafts, said gearing having a fixed ratio such that one revolution of said second cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal.

4. In a recording mechanism for a startstop telegraph, the combination of a selecting cam shaft, means for intermittently rotating said cam shaft, a single rotating member responsive to received signal impulses, connecting gearing between said member and said cam shaft, a pivotally-mounted rocker actuated by said rotary member in dependence upon the kind of signal impulse received and setting mechanism controlled by said rocker, said gearing having mounted to rotate and to be shifted in the direction of its axis into either of two positions depending upon the signal impulse received, connecting gearing between said selecting cam shaft and said relay cam shaft, a cam mounted on said relay cam shaft, a pivotally-mounted rocker furnished with two projections operable respectively by said cam in the two axial positions of said relay cam shaft and setting mechanism controlled by said rocker, the ratio of said gearing being such that onerevolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal.

6. In a recording mechanism for a-start-stop telegraph, the combination of a selecting cam shaft, means for intermittently rotating said cam shaft, a mechanical relay cam shaft mounted to rotate and to be shifted in the direction of its axis into either of two positions depending upon the signal impulse received, connecting-gearing between said selecting cam shaft and said relay cam shaft, a cam mounted on said relay cam shaft, a pivotally-mounted rocker furnished with two projections operable respectively by said cam in the two axial positions of said relay cam shaft, a plurality of permutation bars and setting mechanism for said permutation bars operable by said selecting cam shaft and controlled in accordance with the position of said rocker, the ratio of said gearing being such that one revolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal.

'7. In a recording mechanism for a start-stop telegraph, the combination of a selecting cam shaft, a plurality of cams mounted thereon in varying angular relationship, means for intermittently rotating said cam shaft, a mechanical relay cam shaft mounted to rotate and to be shifted in the direction of its axis into either of two positions depending upon the signal impulse received, a cam mounted on said relay cam shaft, a pivotally-mounted rocker furnished with two projections operable respectively by said cam in the two axial positions of said relay cam shaft, a plurality of slidably-mounted permutation bars, a plurality of pairs of pivoted levers, each pair in operative relationship with one of said selecting cams and connected to one of said permutation bars so as to be selectively operated by said selecting cam in dependence upon the position of said rocker to actuate the respective permutation bars and connecting gearing inter-connecting said selecting cam shaft and said relay cam shaft, the ratio of said gearing being such that one revolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal. 8. In a recording mechanism for a start-stop telegraph, the combination of a selecting cam shaft, means for intermittently rotating said cam shaft, a mechanical relay cam shaft mounted to rotate and to be shifted in the direction of its axis 10 into either' of two positions, a cam mounted on said relay cam shaft, a single receiving magnet having an armature formed with a cam surface movable into and out of operative relationship with said relay cam shaft to effect axial shifting l of the latter upon rotation of same, a pivotallymounted rocker furnished with two projections operable respectively by said cam in the two axial positions of said relay cam shaft, setting mechanism controlled by said rocker and connecting gearing between said selecting cam shaft and said relay cam shaft, the ratio of said gearing being such that one revolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal.

9. In a recording mechanism for a start-stop telegraph, the combination of a selecting cam shaft, means for intermittently rotating said cam shaft, a mechanical relay cam shaft mounted to rotate and to be shifted in the direction of its axis into either of two positions, a cam mounted on said relay cam shaft, a single receiving magnet r having an armature formed with a. cam surface 30 movable into and out of operative relationship with said relay cam shaft to effect axial shifting of the latter upon rotation of same, a yieldinglymounted cam member located to return said relay cam shaft axially upon further rotation of same,

a pivotally-mounted rocker furnished with two projections operable respectively by said cam in the two axial positions-of said relay cam shaft, setting mechanism controlled by said rocker and connecting gearing between said selecting cam shaft and said relay cam shaft, the ratio of said gearing being such that one revolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding'the time period of all the code impulses of one complete character signal.

10.In a recording mechanism for a start-stop telegraph, the combination of a selecting cam shaft, a plurality of cams mounted thereon, means for intermittently rotating said cam shaft, a mechanical relay cam shaft mounted to rotate and to be shifted in the direction of its axis into either of two positions depending upon the signal impulse received, a cam mounted on said relay cam shaft, 9. stop member mounted upon said selecting cam shaft, a detent in operative relation with said stop member, a single receiving magnet, means in operative relationship with the armature of said magnet for releasing said detent, and freeing said selecting cam shaft until re-engaged by said stop member, said means being constituted to be moved out of relationship with said armature when actuated thereby, a pivotallymounted rocker furnished withtwo projections operable respectively by said cam in the two axial positions of said relay cam shaft, setting mechanism controlled by said rocker and connecting gearing between said selecting cam shaft and said relay cam shaft, the ratio of said gearing being such that onerevolution of said relay cam shaft occupies a time equal to an integral number of the signal impulse periods but not exceeding the time period of all the code impulses of one complete character signal,

RONALD GEORGE GRIFFITH. 

